Introduction to Computer Engineering CS/ECE 252, Spring 2008 Prof. David A. Wood Computer Sciences Department University of Wisconsin – Madison Adapted from Prof. Hill’s notes

Chapter 1 Welcome Aboard Slides based on set prepared by Gregory T. Byrd, North Carolina State University

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-3 Computer System: Layers of Abstraction Software Hardware Application Program Language Instruction Set Architecture (and I/O Interfaces) Microarchitecture Circuits Devices Algorithms Problem

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-4 Big Idea #1: Universal Computing Device All computers, given enough time and memory, are capable of computing exactly the same things. == PDA Workstation Supercomputer

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-5 Turing Machine Mathematical model of a device that can perform any computation – Alan Turing (1937) ability to read/write symbols on an infinite “tape” state transitions, based on current state and symbol Every computation can be performed by some Turing machine. (Turing’s thesis) T add a,ba+b Turing machine that adds T mul a,bab Turing machine that multiplies

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-6 Universal Turing Machine Turing described a Turing machine that could implement all other Turing machines. inputs: data, plus a description of computation (Turing machine) U a,b,c c(a+b) Universal Turing Machine T add, T mul U is programmable – so is a computer! instructions are part of the input data a computer can emulate a Universal Turing Machine, and vice versa Therefore, a computer is a universal computing device!

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-7 Turing Machine Example Goal: Find a sequence ‘111’ on the input tape. Input: Tape with sequence of 0s and 1s, terminated by a blank character  Output: Tape contains all 0s, except a single 1 indicating position of first sequence (if any). Tape Head (Read and Write the Tape) State: A  Current symbol Action Table Turing Machine

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-8 TM Example Action Table StateSymbolTapeNext State A  --Halt A0Print 0Move RightA A1Print 0Move RightB B  --Halt B0Print 0Move RightA B1Print 0Move RightC C  --Halt C0Print 0Move RightA C1Print 1Move RightD D  --Halt D0Print 0Move RightD D1Print 0Move RightD

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-9 From Theory to Practice In theory, computer can compute anything that’s possible to compute given enough memory and time In practice, solving problems involves computing under constraints. time  weather forecast, next frame of animation,... cost  cell phone, automotive engine controller,... power  cell phone, handheld video game,...

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Big Idea #2: Transformations Between Layers How do we solve a problem using a computer? A systematic sequence of transformations between layers of abstraction. Problem Algorithm Program Software Design: choose algorithms and data structures Programming: use language to express design Instr Set Architecture Instr Set Architecture Compiling/Interpreting: convert language to machine instructions

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Deeper and Deeper… Instruction Set Architecture Instruction Set Architecture Microarch Circuits Processor Design: choose structures to implement ISA Logic/Circuit Design: gates and low-level circuits to implement components Devices Process Engineering & Fabrication: develop and manufacture lowest-level components

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Descriptions of Each Level Problem Statement stated using "natural language" may be ambiguous, imprecise Algorithm step-by-step procedure, guaranteed to finish, deterministic definiteness, effective computability, finiteness Program express the algorithm using a computer language high-level language, low-level language Instruction Set Architecture (ISA) specifies the set of instructions the computer can perform data types, addressing mode

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Descriptions of Each Level (cont.) Microarchitecture detailed organization of a processor implementation different implementations of a single ISA Logic Circuits combine basic operations to realize microarchitecture many different ways to implement a single function (e.g., addition) Devices properties of materials, manufacturability

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Many Choices at Each Level Solve a system of equations Gaussian elimination Jacobi iteration Red-black SORMultigrid FORTRANCC++Java Intel x86Sun SPARCCompaq Alpha Pentium IIPentium IIIAMD Athlon Ripple-carry adderCarry-lookahead adder CMOSBipolarGaAs Tradeoffs: cost performance power (etc.)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display What’s Next Bits and Bytes How do we represent information using electrical signals? Digital Logic How do we build circuits to process information? Processor and Instruction Set How do we build a processor out of logic elements? What operations (instructions) will we implement? Assembly Language Programming How do we use processor instructions to implement algorithms? How do we write modular, reusable code? (subroutines) I/O, Traps, and Interrupts How does processor communicate with outside world?